This application claims the benefit of Danish Application No. PA 2004 03035filed Jun. 30, 2004and PCT/DK2005/000445filed Jun. 30, 2005, which are hereby incorporated by reference in their entirety.
The present invention concerns a lubricating system that includes a method and an installation for lubricating the cylinder faces in large diesel engines, particularly marine engines, including at least one lubricating apparatus with a number of piston pumps which via connecting lines are connected with and feed various lubricating points disposed in the walls of the cylinders.
The lubricating apparatuses are traditionally designed as pumping units which are mounted in close association with respective cylinders, and which are connected with a feeding reservoir for lubricating oil and with lubricating points in the form of oil injection nozzles at different points on the cylinder wall. Each pump unit includes a plurality of piston pumps that feed various lubricating points with oil, and which are driven by a common rotating control shaft with cams applied thereon. At the rotation of the shaft, the cams with pressing heads act on respective axially displacing pistons which are spring biased in direction towards the control shaft, so that the pistons at the rotation of the shaft will perform reciprocating movements for activating the pistons of the piston pumps.
For many years, lubricating apparatuses have operated under the condition that the discharge pressure from the piston pumps was not to be very great, as it is a fixed standard that the oil is to be injected into the cylinder during the upwards return stroke of the engine piston, i.e. during the compressing action, however before the subsequent power stroke by the ignited combustion. Hereby, it has been necessary to operate with injection or pump pressures of the magnitude 10 bar.
In recent years it has been proposed to increase the efficiency of the lubrication by injecting the oil through pressurised atomising nozzles for achieving oil mist lubrication during the upwards movement of the piston. However, hereby the oil is applied a far higher pressure for ensuring fine atomisation through atomising nozzles, e.g. a pressure up to 100 bar or more.
Lubricating points will thus, as mentioned in the present application, include oil injecting nozzles and/or pressurised atomising nozzles.
In both systems, the control shaft is driven through a direct or indirect mechanical coupling with the crankshaft of the engine, whereby it is possible to provide power for the activation of pumps and at the same time to achieve synchronisation between the crankshaft of the engine and the control shaft of the lubricating apparatus.
A pump unit may e.g. include a box-shaped apparatus housing, from where connecting pipes extend to the lubricating points on the associated engine cylinder, e.g. in a number of 6-24.
The pistons are traditionally operated by means of activation cams/rocker arms on a through-going control shaft which is rotated synchronously with the crankshaft of the engine. The pistons are spring biased towards the activation cams. There is provided a set screw defining the extreme position of an associated activation cam. The set screws may be operated for determining individual operative strokes of the pistons and thereby the associated yield of the individual piston pumps.
By lubrication according to the invention, it is possible for the user to operate with controlling injection timing for a synchronised lubrication, which is timed according to the rotation of the crank, or unsynchronised cylinder lubrication, i.e. a cylinder lubrication that does not depend on the rotation and angular position of the crank.
Furthermore, there is an increasing demand for a flexible and easy adjusting of the controlled feeding cylinder lubrication oil portion for the immediate demand of the engine depending on diverse measurable engine parameters. It is also desirable to adjust the timing concurrently with the actual operating situation of the engine in a flexible way. All these adjustments are preferably to be controlled centrally.
Driving the lubricating apparatuses synchronously with the engine speed is electronically feasible, but extensive and costly. With such a system, the timing can be changed immediately. Changing the fed cylinder lubricating oil portion is, however, more difficult to control.
As the cylinder lubricating oil is to be dosed with one portion per engine revolution, the only possibility of adjusting the dosage is to change the stroke of the pumps. A system for this purpose is e.g. described in DK patent application 4998/85. This system is operated by a cam disk mechanism for adjusting the pump stroke in dependence on the engine load. Changing this dependence may only be effected by changing the cam disks with other cam disks with a different transfer function.
It has also been proposed to adjust the pump stroke by means of a controllable motor, e.g. a step motor. This has been used for point lubrication, but it is difficult to establish in connection with conventional lubricating apparatuses. Such a system is e.g. disclosed in International Patent Application no. WO 02/35068 A1.
Moreover, from DE 28 27 626 is also known a lubricating system based on lubricating oil being supplied in measured quantities at predetermined time intervals through apertures in the cylinder wall. There is no indication here of stepless control of the dosage to be performed at individual lubricating points.
In connection with traditional cylinder wall lubrication, it has hitherto been the practice to use simple spring-biased check valves that can resist the internal pressure in the cylinder, but which yield to a slightly higher external injection pressure. However, in connection with pressurised atomised injection, it is desirable and necessary that the valve system opens only at a much higher oil pressure in order that the oil injection can assume the character of a pressurised atomising injection right from the beginning. We are hereby speaking of a pressure differential factor of up to several hundred percent.